Date: Thu, 9 Jan 2014 22:20:04 GMT From: "Eugene M. Kim" <20080111.freebsd.org@ab.ote.we.lv> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/185619: [VNET] Name conflict not checked when a child vnet goes away and returns its interface(s) back to the parent Message-ID: <201401092220.s09MK41t052854@oldred.freebsd.org> Resent-Message-ID: <201401092230.s09MU0Ph049031@freefall.freebsd.org>
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>Number: 185619 >Category: kern >Synopsis: [VNET] Name conflict not checked when a child vnet goes away and returns its interface(s) back to the parent >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Thu Jan 09 22:30:00 UTC 2014 >Closed-Date: >Last-Modified: >Originator: Eugene M. Kim >Release: 11-CURRENT >Organization: AstralBlue >Environment: FreeBSD hydrogen.astralblue.net 11.0-CURRENT FreeBSD 11.0-CURRENT #1 r260314: Sun Jan 5 17:53:02 UTC 2014 root@hydrogen.astralblue.net:/usr/obj/usr/src/sys/GENERIC-IPSEC-VIMAGE amd64 >Description: Each vnet has its own namespace for network interfaces. As a result, two network interfaces may have the same name if they belong to distinct vnets. When one of these interfaces tries to move into the other's vnet, the name conflict should - and does - block the operation, except in one case: When a child vnet goes away and returns its interfaces to its parent vnet, the name conflict is not checked and the parent vnet ends up having both interfaces of the same name. This confuses various tools such as ifconfig(8). >How-To-Repeat: The first scenario shown below renames two epair(4) interfaces as "jnet" (one renamed in a parent vnet, another renamed in a child vnet), then destroys the child vnet to bring its jnet interface back to the parent. ifconfig(8) output merges these two interfaces into one block (shown by two MAC addresses). root@hydrogen:~ # jail -c name=test vnet persist root@hydrogen:~ # ifconfig epair create epair0a root@hydrogen:~ # ifconfig epair0a epair0a: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:40:00:04:0a nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active root@hydrogen:~ # ifconfig epair0b epair0b: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:90:00:05:0b nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active root@hydrogen:~ # ifconfig epair0a name jnet root@hydrogen:~ # ifconfig epair0b vnet test root@hydrogen:~ # jexec test ifconfig epair0b name jnet root@hydrogen:~ # jail -r test root@hydrogen:~ # ifconfig lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384 options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6> inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3 inet 127.0.0.1 netmask 0xff000000 nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL> jnet: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:40:00:04:0a ether 02:ff:90:00:05:0b nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active root@hydrogen:~ # ifconfig jnet destroy root@hydrogen:~ # The second scenario shown below creates two vnets and two epair(4) pairs (one pair for each vnet), injects the "b" end of each pair into the corresponding vnet then renames it as "jnet", then destroys the two vnets, showing the parent vnet ending up with both jnet interfaces. At the end, "ifconfig jnet destroy" can be done twice: The first command picks and destroys one of the two pairs. root@hydrogen:~ # ifconfig epair create epair0a root@hydrogen:~ # ifconfig epair create epair1a root@hydrogen:~ # jail -c name=test1 vnet persist root@hydrogen:~ # jail -c name=test2 vnet persist root@hydrogen:~ # ifconfig epair0b vnet test1 root@hydrogen:~ # jexec test1 ifconfig epair0b name jnet root@hydrogen:~ # ifconfig epair1b vnet test2 root@hydrogen:~ # jexec test2 ifconfig epair1b name jnet root@hydrogen:~ # jail -r test1 root@hydrogen:~ # jail -r test2 root@hydrogen:~ # ifconfig em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MAGIC,VLAN_HWTSO> ether 74:d0:2b:13:66:fc inet 10.0.0.11 netmask 0xffffff00 broadcast 10.0.0.255 inet6 fe80::76d0:2bff:fe13:66fc%em0 prefixlen 64 scopeid 0x1 inet6 2001:470:1f05:155:76d0:2bff:fe13:66fc prefixlen 64 autoconf inet6 2002:43bc:72e6:1:76d0:2bff:fe13:66fc prefixlen 64 autoconf nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL> media: Ethernet autoselect (1000baseT <full-duplex>) status: active em1: flags=8c02<BROADCAST,OACTIVE,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MAGIC,VLAN_HWTSO> ether 74:d0:2b:13:6b:43 nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet autoselect status: no carrier lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384 options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6> inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3 inet 127.0.0.1 netmask 0xff000000 nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL> epair0a: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:40:00:04:0a nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active epair1a: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:40:00:06:0a nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active jnet: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=8<VLAN_MTU> ether 02:ff:90:00:05:0b ether 02:ff:90:00:07:0b nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>) status: active root@hydrogen:~ # ifconfig jnet destroy root@hydrogen:~ # ifconfig jnet destroy root@hydrogen:~ # >Fix: One of the following would fix the problem (among other approaches I cannot think of): Option 1: Give the returned interface a random, unique name. Option 2: When injecting an interface into a child vnet, leave a "shadow" of its name in the parent vnet. Don't let other interfaces in the parent vnet take the shadowed name, and give the shadowed name to the moved interface when it returns from the child vnet. Option 3: Block destruction of a vnet if doing so would cause a name conflict in the parent vnet. Option 3 opens a bigger problem and is probably impractical, as such blocking should be cascaded to and handled by the triggering event such as jail destruction, blocking which is probably a bad idea. Option 1 is simpler, but the resulting behavior is random/nondeterministic and makes interface tracking harder. Option 2 is more predictable and deterministic, at the cost of more complex implementation. And it doesn't cover the case of pseudo-interfaces created locally inside a vnet, because such interfaces have no shadowed name in the parent vnet; falling back to option 1 would be one way to solve this. >Release-Note: >Audit-Trail: >Unformatted:
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